Step-by-step explanation:
It seems like there might be a syntax error or missing information in the expression you've provided. The formula appears to be incomplete or unclear.
If you meant to express a formula to find the sum of the first \( n \) terms of an arithmetic sequence, typically denoted as \( S_n = \frac{n}{2}(a_1 + a_n) \), where \( a_1 \) is the first term and \( a_n \) is the \( n \)th term, please provide the correct equation or additional information, and I'd be happy to help you solve it.
